One beneficiary has died on my Mother's will. Now what?

My mother did not think she would outlive her children. According to her will, the spouse of the beneficiery will get nothing. However this one spouse of the deceased beneficiery (died from copd) is special because she lived close to my mother and assumed to care for her. After awhile I realized she was burnt out and I moved my mother's care to a sister who is a retired nurse. My mother recently turned a bad corner and is completely bedridden. If my mother died we think this one spouse should get some money. But my mother is too far gone to sign anything and if she could, she doesn't remember the care that spouse gave her. I am the POA and executor but I am not allowed to update beneficieries. I could build up money in the checking account to give to her but the bank will throw me into probate if there is over $10,000 in there and I need some of that for a headstone and such. I am contacting the other beneficieries (one brother and two other sisters) to see if I can get agreement on this one spouse. We 3 sisters seem in agreement to give our half-brother's share to his wife, but have yet to here from the brother. It must be unamious. Any ideas of where to store the money for her without my mother's signature and not in her checking account?